In present day telecommunications networks, an incoming call, dialed by a calling party to a called party, enters the network at an ingress switch serving the calling party. The ingress switch routes the call to a terminating switch serving the called party, either directly, or through one of more intermediate (via) switches. In order to route a call, each switch typically performs a translation to establish a route list of trunks capable of carrying the call to the next switch. Often, multiple trunks link the various switches in a network, so call routing not only involves selecting the next switch, but also selecting the particular idle trunk linking the switches. Presently, each switch makes its own routing decisions. Thus, in a telecommunications network that embodies multiple switches using different technologies, such as Circuit-switching, ATM switching or IP routing, often from different vendors, making routing changes becomes very cumbersome. Unfortunately, with growing demand for telecommunications services, routing changes occur frequently, as new switches are deployed.
In an effort to overcome the difficulty of having to update existing switches in a telecommunications network, there currently exist proposals for employing a new exterior processor with each existing switch to make call control decisions for implementation by the existing switches which then perform switch fabric functions. For example, U.S. Pat. No. 6,041,117, issued in the name of Frank Androski et al., and assigned to AT&T Corp., discloses a distributed communications system in which individual switching systems are controlled by an exterior switch processing platform. The switch processing platform performs call-associated logic functions, such as address translation and routing functions previously performed by the internal switch call processor, whereas each switch performs switch fabric (call connection) functions, including reserving, connecting and releasing trunks.
U.S. Pat. No. 5,590,181, issued in the name Steven Hogan et al. discloses a call processing system comprised of at least one network switch linked to a network control processor that makes call handling and routing determinations for that switch. Only the audio portion of a call is received at a switch for transmission to a subsequent switch. The network control processor makes all call processing and call-handling decisions.
The aforementioned Androski et al. '117 patent and the Hogan et al '181 patent employ call processing platforms that make call logic decisions and thereafter provide the information to each switch. Implementing these techniques requires the development of new interfaces to allow present-day switches to receive the information from the separate call processing application platform since present day switches are not presently adapted to do so. Modifying present day switches to accept such special interfaces could prove expensive and time consuming.
Thus, there is a need for a technique for achieving centralized call routing that overcomes the disadvantages of the prior art.